Phosphorus biological cycle in the different Emph

Authors: Zhigao Sun Xiaojie Mou Hanqin Tian Hongli Song Huanhuan Jiang Jinyong Zhao Wanlong Sun Wenguang Sun

Publish Date: 2012/11/15

Volume: 69, Issue: 8, Pages: 2595-2608

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Abstract

Much uncertainty exists in the phosphorus P cycle in the marshes of the intertidal zone This study explored the P cycling in the two Suaeda salsa marshes middle S salsa marsh MSM and low S salsa marsh LSM of the Yellow River estuary during April 2008 to November 2009 Results showed seasonal fluctuations and vertical distributions of P in different S salsa marsh soils and variations in P content in different parts of plants due to water and salinity status The N/P ratios of the different S salsa were 987 ± 123 and 1573 ± 177 respectively indicating that plant growth in MSM was limited by N while that in LSM was limited by both N and P The S salsa litter in MSM released P to the environment throughout the year while that in LSM immobilized P from the environment at all times The P absorption coefficients of S salsa in MSM and LSM were very low 00010 and 00001 respectively while the biological cycle coefficients were high 0739 and 0812 respectively The P turnovers among compartments of MSM and LSM showed that the uptake amounts of roots were 04275 and 00469 g m−2 year−1 and the values of aboveground parts were 11702 and 01833 g m−2 year−1 the retranslocation quantities from aboveground parts to roots were 08544 and 01452 g m−2 year−1 the translocation amounts from roots to soil were 00137 and 00012 g m−2 year−1 the translocation quantities from aboveground living bodies to litter were 03157 and 00381 g m−2 year−1 and the annual return quantities from litter to soil were less than 00626 and −00728 g m−2 year−1 minus represented immobilization respectively P was an important limiting factor in S salsa marshes especially in LSM S salsa was seemingly well adapted to the lownutrient condition and the vulnerable habitat and the nutrient enrichment due to the import of N and P from the Yellow River estuary would be a potential threat to the S salsa marshesPhosphorus P has been regarded as a common limiting nutrient in ecosystems which plays an important role in many biogeochemical processes Hinsinger 2001 Zhang et al 2005 such as participating in the composition of many Pcontaining compounds nucleic acid phospholipid ribonucleotide and adenosine triphosphate controlling the metabolism of carbohydrates in the photosynthesis process and enhancing the stressresistance and adaptation of plants Lu 2003 P also has significant effects on other nutrient carbon C nitrogen N cycles Newman and Lynch 2001 Tian et al 2010 water body eutrophication and plant productivity Compton et al 2000 Hinsinger 2001 The P cycle is one of the most complex cycles in wetland ecosystems which is responsible for a series of important biogeochemical processes Qin 2008 The productivity and trophic status of wetlands are usually dependent on the concentration of P in waters or soils Wetlands have often been called the ‘green filter’ for their P retention capability and water purification capability Coelho et al 2004 and about 80–90  of P is stored in soils due to the long turnover time of P in wetland ecosystems JiménezCárceles and ÁlvarezRogel 2008There has been intensely increasing interest in understanding the P cycle in wetland ecosystems because high input of nutrient N P into wetlands along with oxic surface and anoxic subsurface zones potentially allow P to play a critical role in the biogeochemistry of wetlands Walbridge 2000 Many studies have been conducted on the processes of the P cycle in different wetland ecosystems such as salt marshes Coelho et al 2004 Bai et al 2007 freshwater marshes Hogan et al 2004 Dunne et al 2007 Zhang et al 2011 and peatlands Niedermeier and Robinson 2009 Tidal marshes are very important in coastal zones which are sensitive to global climate change and human activities In general most of the P in tidal marshes is bound to clay and silt particles or is precipitated as mineral P and changes in physical conditions such as oxygen concentration salinity or pH can alter this balance Qin 2008 However information on the processes of the P cycle in tidal marshes remains limited In addition current studies mostly focus on a certain process of the P cycle while systemic and synthetic studies are lacking The compartment model has been widely and successfully applied in previous research and is a common approach to study the element cycles of ecosystems Reuss and Innis 1977 Wallance et al 1978 Most compartment model studies have however focused on grassland ecosystems Li and Redmann 1992 Li et al 2003 forest ecosystems Liu and Yu 2005 Wu et al 2006 and freshwater marsh ecosystems Sun and Liu 2007 Liu and Li 2008 and information on the P cycle of tidal marshes remains scarceThe Yellow River is well known as a sedimentladen river Every year approximately 105 × 107 tons of sediment is carried to the estuary Cui et al 2009 and deposited in the slow flowing landform resulting in vast floodplain and special marsh landscape Xu et al 2002 Sediment deposition is an important process for the formation and development of tidal marshes in the Yellow River Delta The deposition rate of sediment in the Yellow River not only affects the formation rate of tidal marshes but also to some extent influences water or salinity status and the succession of plants Tidal marsh is the main marsh type with an area of 9648 km2 accounting for 6306  of the total area of the Yellow River Delta Cui et al 2009 Suaeda salsa is the most prevalent plant in the tidal marsh of the Yellow River estuary As a pioneer plant it has strong adaptations to environmental stresses such as high salinity flooding and sediment burial Han et al 2005 Suaeda salsa generally germinates in late April blooms in July matures in late September and completely dies in late November Gu 1998 In the S salsa distribution area two phenotypes are generally formed due to the differences of water and salinity conditions in tidal marshes In the middle marsh the S salsa is unfrequently and irregularly affected by the tide so the salinity of sediment is low electrical conductivity 0–5 cm 558 ± 280 mS cm−1 Mou et al 2010 The leaf and stem of S salsa are green during the growth period and the plant is tall Wang et al 2006 In the low marsh the S salsa is frequently affected by the tide so the salinity of sediment is very high electrical conductivity 0–5 cm 1807 ± 043 mS cm−1 Mou et al 2010 The leaf and stem of S salsa are generally red–violet and the plant is very short Wang et al 2006 However information on elemental biogeochemical processes of the tidal marshes in the Yellow River estuary is limited and the systemic and comparative studies on the P cycles of the two S salsa marshes are still lackingIn this paper the P biological cycle of the two S salsa marshes in the intertidal zone of the Yellow River estuary was systemically and comparatively studied The S salsa marsh was divided into four P compartments including aboveground living body root litter and soil The purposes of this paper were i to determine the distribution characteristics of P in the plantsoil system ii to study the P turnovers among the compartments of S salsa marsh and iii to establish the P biological cycle compartment pattern of S salsa marshes and evaluate the P cycle statusThis study was conducted from April 2008 to November 2009 at two experimental plots in the S salsa distribution area middle S salsa marsh MSM 37°45′570″N 119°09′407″E low S salsa marsh LSM 37°46′389″N 119°09′414″E in the intertidal zone of the Yellow River estuary located in the Nature Reserve of Yellow River Delta 37°35′N–38°12′N 118°33′E–119°20′E in Dongying City Shandong Province China The nature reserve is of typical continental monsoon climate with distinctive seasons summer is warm and rainy while winter is cold The annual average temperature is 121 °C the frostfree period is 196 days and the effective accumulated temperature is about 4300 °C Annual evaporation is 1962 mm and annual precipitation is 5516 mm with about 70  of precipitation occurring between June and August The soils in the study area are dominated by intrazonal tide soil and salt soil Tian et al 2005 and the main vegetations include Phragmites australis S salsa Triarrhena sacchariflora Myriophyllum spicatum Tamarix chinensis and Limoninum sinenseLitter production aboveground biomass AGB and belowground biomass BGB were determined using quadrat method 50 cm × 50 cm five replications at the two experimental plots from May to November in 2008 with a sampling frequency of 20 days On the sampling dates the aboveground part of plant was clipped near the ground and the stem leaf and standing dead litter were separated immediately in the laboratory The new litter distributed in the quadrat was also collected Roots in the quadrat were dug out and washed carefully All samples were weighed after being dried at 80 °C for 48 h In the growing season because little parts of the plant or the litter could be carried away or redistributed in tidal marshes during the ebb and flow the AGB and litter production were standing cropsAll soil and plant samples were ground 025 mm using a Wiely mill and analyzed for TC TN contents by element analyzer Elementar Vario Micro German and TP content by molybdateascorbic acid colorimetry digested by H2SO4–H2O2 The Committee of Agrochemistry of the Chinese Society of Soil Science 1983

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